Liquid crystal display panels including recesses for majority of spacers

ABSTRACT

A liquid crystal display panel comprises a color filter substrate, a thin film transistor array substrate, and a liquid crystal layer sealed between the two substrates. The color filter substrate has a plurality of first spacers and a plurality of second spacers thereon. The thin film transistor array substrate has a plurality of recesses for containing the second spacers. The ratio of the number of the second spacers to the number of the first spacers is between about 10 and about 90.

RELATED APPLICATIONS

The present application is based on, and claims priority to, TaiwanApplication Serial Number 95129816, filed Aug. 14, 2006, the disclosureof which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention is related to a structure of a liquid crystaldisplay panel.

BACKGROUND OF THE INVENTION

One drop filling (ODF) process is used as a new generation liquidcrystal manufacturing technique. The ODF process is widely used for massproduction of liquid of crystal because of its advantage of largelyshortening the time required to fill liquid crystal. Nevertheless, abottle neck of the ODF process is its narrow tolerance of the amount ofthe filled liquid crystal. In detailed description, tolerance of theamount of the filled liquid crystal is very narrow under lowtemperature. Vacuum bubbles are easily generated under low temperaturewhen the amount of the filled liquid crystal is not accurate, orphoto-resist spacers located between the color filter substrate and TFTarray substrate are diverged (in other word, vacuum bubble is a vacuumspace generated by liquid crystal volume shrinkage under lowtemperature). Methods for increasing the tolerance of the amount of thefilled liquid crystal include, selecting a softer material forphoto-resist spacers, decreasing the contact area between thephoto-resist spacers and TFT array substrate and so on. These methodsallow the distance between liquid crystal cells to be modulable in themanufacturing process to increase tolerance of the amount of the filledliquid crystal.

SUMMARY OF THE INVENTION

For the purpose of increasing the tolerance of the amount of filledliquid crystal in the ODF process and the purpose of increasing pressureresistivity of the liquid crystal display panel, the embodiments of thepresent invention provide a liquid crystal display panel with enoughpressure resistivity. The display panel comprises a color filtersubstrate, a TFT array substrate and a liquid crystal layer sealedbetween both substrates. A plurality of first spacers and a plurality ofsecond spacers are located on the color filter substrate. A plurality ofrecesses is located on the TFT array substrate for containing the secondspacers while the two substrates are sealed face to face. The ratio ofthe number of second spacers to the number of first spacers is from 10to 90.

In another embodiment, the present invention provides a liquid crystaldisplay panel. The display panel comprises a color filter substrate, aTFT array substrate and a liquid crystal layer sealed between bothsubstrates. A plurality of spacers is located on the color filtersubstrate. A plurality of recesses is located on the TFT array substratefor containing a portion of the spacers while the two substrates aresealed face to face. The ratio of the number of recesses to the numberof spacers is from 90% to 98%.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates a cross-sectional view of one embodiment of thepresent invention;

FIG. 2 illustrates a cross-sectional view of the liquid crystal displaypanel shown in FIG. 1 under pressure; and

FIG. 3 illustrates a relationship scheme of deformation of the firstspacer vs. the force applied on the liquid crystal display panel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the present ODF process, liquid crystal is dropped on the colorfilter substrate (or TFT substrate) in vacuum and glue is coated on therim of the TFT substrate (or color filter substrate). Then, the colorfilter substrate and the TFT substrate are assembled together. A liquidcrystal display panel is accomplished by removing the vacuum source andadmitting atmospheric air to compress the color filter substrate or TFTsubstrate.

If the photo-resist spacers can not provide enough deformation when theamount of the filled liquid crystal is not accurate or the height of thespacers is not as expected, then the vacuum bubbles will be generatedbecause the height of the spacers and the amount of the filled liquidcrystal can not match the space in the liquid crystal cell between thetwo substrates. Although a softer photo-resist spacer can be used tosolve the problem caused by the mismatch between the height of thespacers and the filled liquid crystal, the softer photo-resist spacersdo not have enough pressure resistivity so that the yield of liquidcrystal display panel is decreased because defects are easily generatedby the compressing force required for assembling the module.

An embodiment of the present invention provides a liquid crystal displaypanel. FIG. 1 illustrates a cross-sectional view of one embodiment ofthe present invention. Refer to FIG. 1, a liquid crystal display panel100 comprises a color filter substrate 102, a TFT substrate 104, and aliquid crystal layer 106 sealed between the color filter substrate 102and the TFT substrate 104. The color filter substrate 102 has aplurality of first spacers 108 and a plurality of second spacers 110.The TFT substrate 102 has a plurality of recesses 112. The location ofthe recesses 112 corresponds to the position of the second spacers 110.The size of the recess 112 is proper for containing the second spacer110. The color filter substrate 102 further comprises a black matrixlayer 103. The preferred location of the second spacers 110 is on theblack matrix layer 103 to avoid possible light leakage.

The depth of the recesses is from 0.2 μm to 0.8 μm. The height of thefirst spacers 108 and the second spacers 110 is from 1 μm to about 10μm. The ratio of the number of the second spacers 110 to the number ofthe first spacers is from 10 to 90. The location of the recesses 112corresponds to the position of the second spacers 110 for providingsupporting force when an external force is applied upon the liquidcrystal display panel.

In the present embodiment, the first spacers 108 and the second spacers110 may be disposed on the color filter substrate (or the TFT arraysubstrate) while the recesses are formed on the TFT array substrate (orthe color filter substrate).

In the present embodiment, the first spacers 108 and the second spacers110 are different in shape, height or both. The first spacers 108 arelocated between the color filter substrate 102 and the TFT substrate104. The TFT substrate 104 has recesses 112 corresponding to theposition of the second spacers 110. Δh is defined as the distancebetween the bottom (top) portion of the recesses 112 and the secondspacers 110 as shown in FIG. 1. The shape of the second spacers 110 canbe cylinder, cuboid, cone-shape, or other pillar like shape. The widthof the cross section of the second spacers 110 is from 9 μm to 11 μm.

Referring to FIG. 2, FIG. 2 illustrates a cross-sectional view of theliquid crystal display panel shown in FIG. 1 under pressure. When anexternal force 10 provided by air pressure is applied upon the liquidcrystal display panel while the volume of the liquid crystal layershrinks at low temperature, the first spacers 108, such as thephoto-resist spacers illustrated in the FIG. 1 will be elasticallydeformed and become the spacers 108′ illustrated in the FIG. 2. Thedistance between the color filter substrate 102 and TFT substrate 104 isthus decreased so that vacuum bubbles can be avoided. The tolerance ofthe amount of the filled liquid crystal can be increased to allow theamount of the filled liquid crystal and the height of the spacers to bewell matched and vacuum bubbles can be avoided when the change of liquidcrystal volume or the drifting of the height of the photo-resist spacersoccurs.

Referring to FIG. 1 and FIG. 2, the top of the second spacers 110 do notcontact with the bottom (top) surface of the recesses 112 until theshortened distance between the color filter substrate 102 and TFTsubstrate 104 reaches Δh. The recess 112 contains the second spacer 110.The cross section area of the recess 112 is equal to or slightly largerthan the cross section area of the second spacer 110. For example, inthe present embodiment, a height of the first spacer 108 may besubstantially equal to that of the second spacer 110. For example, inthe present embodiment, the cross section area of the recess 112 may beslightly larger than a smallest or a largest cross section area of thesecond spacer 110.

FIG. 3 illustrates a relationship scheme of deformation of the firstspacer vs. the force applied on the liquid crystal display panel. Whenan external force 10 provided by the air-pressure is applied upon theliquid crystal display panel while the volume of the liquid crystallayer shrinks at low temperature, the first spacers is elasticallydeformed and the distance between the color filter substrate 102 and TFTsubstrate 104 is decreased. At this moment, the relationship between theshortened distance and the external force applied upon the liquidcrystal display panel 100 is illustrated as the solid line in FIG. 3.When the external force increases, the shortened distance between thecolor filter substrate 102 and TFT substrate 104 reaches Δh and the topof the second spacers 110 contacts with the bottom (top) surface of therecesses 112. The second spacers 110 provide more supporting force toresist the external force. At this moment, the relationship between theshortened distance and the external force applied upon the liquidcrystal display panel 100 is illustrated as the dotted line in FIG. 3.The shortened distance will not be increased anymore when the shorteneddistance reaches the maximum value of the solid line. Therefore, theliquid crystal display panel can resist more pressure. The structuredisclosed in the present embodiment provides higher pressure resistivityto the liquid crystal display panel.

In another embodiment of the present invention, the first spacers andthe second spacers are the same in shape and size. The first spacers andthe second spacers are formed in one lithographic process. The ratio ofthe amount of recesses located on the TFT substrate to the total amountof the spacers is from 90% to 98%.

In the other embodiment of the present invention, the first spacers andthe second spacers may be made from different materials. The firstspacers are made from more elastic material, such as photo-resist andthe second spacers are made from more rigid material, such as siliconoxide, silicon nitride, silicon oxynitride and so on for providing highpressure resistivity to the liquid crystal display panel.

The disclosures of the embodiments of the present invention providedifferent shape designs and locations of spacers. The spacers locatedbetween the TFT substrate and the color filter substrate provide enoughdeformation under the compressing step of the ODF process. Therefore,the tolerance of the amount of the filled liquid crystal can beincreased and the vacuum bubbles can be either decreased or avoided.Furthermore, when a force is applied upon the liquid crystal displaypanel, the distance between the color filter substrate and the TFTsubstrate is decreased and the backup spacers on the color filtersubstrate are inserted in the recesses on the TFT substrate to providemore supporting force. Then, the liquid crystal display panel has higherpressure resistivity.

The spacers are located on one side of the color filter substrate. Thereare two kinds of spacers, major spacers and assistant spacers. The majorspacers and the assistant spacers are the same or different in shape,size or both. The assistant spacers correspond to the recesses locatedon the TFT substrate to provide higher pressure-resistivity to theliquid crystal display panel when the deformation of the major spacersequals to or excesses Δh. Only the major spacers contact with the TFTsubstrate and the color filter substrate when the liquid crystal displaypanel is manufactured. While a force is provided to the liquid crystaldisplay panel, the major spacers are deformed and the deformation of themajor spacers reaches Δh, the assistant spacers begin to providesupporting force. Because the contact area between the spacers and theTFT substrate increases, the resistance to the force from outside isalso increased and the deformation of the spacers will not be increasedany more.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrated of the presentinvention rather than limiting of the present invention. It is intendedto cover various modifications and similar arrangements included withinthe spirit and scope of the appended claims, such as using the design ofarea change between the spacers and substrate to control the deformationof the spacer to achieve the scheme illustrated in FIG. 3; the spacersare located on the black matrix or passive layer of the color filtersubstrate; the recesses are located on any position of the TFT substratefor corresponding the assistant spacers; using halftone mask orcontrolling the energy of the exposure for forming recesses and spacers,and so on, scope of which should be accorded the broadest interpretationso as to encompass all such modifications and similar structure.

1. A liquid crystal display panel, comprising: a first substrate; a plurality of first spacers located on the first substrate; a plurality of second spacers located on the first substrate, wherein a material of the first spacers is more elastic than a material of the second spacers; a second substrate having a plurality of recesses thereon for containing the second spacers; and a liquid crystal layer sealed between the first substrate and the second substrate; wherein a ratio of the number of the second spacers to the number of the first spacers is from 10 to 90, and a depth of the recesses is from 0.2 μm to 0.8 μm.
 2. The display panel of claim 1, further comprising a black matrix disposed on the first substrate, wherein at least one of the first spacers and the second spacers is disposed on the black matrix.
 3. The display panel of claim 1, wherein a height of the first spacers is substantially equal to that of the second spacers.
 4. The display panel of claim 1, wherein a cross section area of each recess is slightly larger than a largest cross section area of each second spacer.
 5. The display panel of claim 1, wherein a cross section area of each recess is slightly larger than a smallest cross section area of each second spacer.
 6. The display panel of claim 1, wherein a cross section area of each recess is slightly larger than a cross section area of each second spacer.
 7. The display panel of claim 1, wherein a height of the first spacers is from 1 μm to 10 μm.
 8. The display panel of claim 1, wherein a height of the second spacers is from 1 μm to 10 μm.
 9. The display panel of claim 1, wherein the material of the first spacers comprises photo-resist.
 10. The display panel of claim 1, wherein the material of the second spacers comprises silicon oxide, silicon nitride, or silicon oxynitride. 